The present invention relates to a process for treating a metal surface. In particular, the present invention relates to a process for treating a metal surface to impart a chemical reactivity thereto.
Techniques of making the metal surface functional have been widely known.
For example, techniques of forming a protective film for physically or chemically protecting the metal surface or a functional film for imparting optical properties (such as coloring, light absorbance, reflectivity, antireflectivity and photoconductivity) have been proposed. These surface treatment techniques can be conducted by various methods wherein a particular chemical substance is applied to the metal surface.
On the contrary, methods of imparting chemical functions such as chemical reactivity to the metal surface are limited. For example, a method of making the surface oxidation-reactive by forming a perovskite layer on the surface of an electrode is well known. The chemical reactivity is due to the surface compound. This reaction proceeds catalytically, but the surface per se is neither reacted nor changed. Namely, there are a few methods capable of imparting the chemical reactivity due to the functional group to the surface so as to cause the surface per se to be involved in the chemical reaction. In other words, there are a few methods of obtaining the surface having an intended distribution of functional groups and each of them has its own defect.
For example, a method wherein the surface is treated with plasma to introduce a functional group into the surface has defects that the treatment should be conducted in vacuo, that the control of the process parameter is troublesome and that an excellent reproducibility cannot be easily obtained by the surface treatment. Further, this method is usually employed for the treatment of a polymer film, but not for the treatment of the metal surface.
The surface treatment with a silane coupling agent has defects that the adhesion is poor because the wettability with the hydrophilic surface is poor, that the control of the reactions such as condensation dehydration on the surface to be treated is not easy and the surface is apt to be stained with the catalyst or the like, and that microscopically, an organic substance is excessive in a part of the inorganic support surface to which the silane coupling agent was applied and, therefore, it is unsuitable for use in applications where a well-balanced lipophilic and hydrophilic property is necessary.
Although it was reported that a hydrophilic functional group is formed on the surface of a silicon rubber by introduction of a heavy ion an expensive apparatus is required and the material to be treated is limited and therefore this method is not popular.